Third Grade Unit Four
Physical Science
Section 1:
TLW describe the motion of objects in terms of speed, direction, and the forces
exerted on the object.
(Gist: Force and Motion)
Enduring Understanding(s)
 A force is a push or pull.
 Pushes or pulls can change the speed or direction of moving objects.
 The position of the observer and object affect the description of motion.
 The shape, size, and weight (mass) of an object can affect its motion.
Essential Questions
 What affects the movement of an object?
 What is a force?
New Vocabulary
around
cause and effect
change in motion
change of direction
force
force strength
gravity
motion
path
slowing down
speeding up
start
stop
through
weight
Concepts & Information
A force is a push (move an object away) or pull (move an object toward). These forces can be
caused by gravity, friction, magnetism, machines or nature (wind and water), muscle power
(people). The amount of force needed to move an object depends on the object’s mass. The
larger the force the greater the change in motion. Forces speed up, slow down, stop, change the
direction of a moving object, or change the shape of the object.
Motion is a change in position.
Motion is the movement of an object from one place to another of physical motion such as
twirling and waving.
The path of motion can be described as moving away from, toward, around, above, below,
behind, between and through an object that is not moving.
The terms north, south, east, and west describe motion with reference to the Earth.
Changes in direction include north, south, east, west, right, left, up, and down.
If forces are equal and opposite, an object will remain at rest. Students just need to observe the
concept, not have to explain it. There may be may forces acting on an object at one time. The
combination results in changes in motion or no motion.
Friction occurs when two objects rub against each other, causing objects in motion to slow down
or stop. Air resistance is a form of friction. Increasing or reducing friction affects the amount of
force needed to move an object. There are times when friction needs to be reduced (ice skating,
automobile motor parts) and times when friction needs to be increased (car brakes, rubber-soled
shoes).
An object at rest tends to stay at rest or an object in motion tends to stay in motion unless a force
acts on it.
A simple machine is a device with few or no moving parts that multiplies and/or changes the
direction of forces and usually makes work easier. The six simple machine types are: lever,
wedge, pulley, wheel and axle, inclined plane, and screw.
An inclined plane is a simple machine used to raise or lower an object with less effort but which
moves the object through a distance on an angle instead of straight up or down; ramp (e.g.,
wheelchair ramp, expressway ramp) .
A lever is a simple machine (bar) used with a fulcrum to pry, raise, or move an object or to
separate objects.
A pulley is a simple machine that uses a wheel with a grooved rim in which a rope or cable can
move to change the direction of the pull to lift the load.
A wedge is a device that tapers to a sharp edge used to separate or cut objects or to adjust
positions of heavy objects (e.g., knife in peanut butter, axe splitting wood, piece of wood or
cardboard put under an uneven bookshelf to make it level).
A wheel and axle is a simple machine used to lift weights by winding a rope or chain onto the
axle as the wheel is turned (e.g., lifting a bucket from a well).
A screw is a simple machine that is a cylinder with an inclined plane wound around it. A screw is
used to raise a load over the threads by applying a small force.
Common Misconceptions
Large objects always exert a greater force than small objects.
When an object is at rest there are no forces acting on it.
Acceleration is speeding up. (Acceleration is also correctly used for slowing down and
changing direction. Do not use the term accelerate with third grade students).
Lesson Ideas:
1. TLW observe and identify real world physical activities that demonstrate motions caused by a push
or pull and the effects of gravity and friction. CCSS/CE(s): P.FM.03.22; P.FM.03.35; P.FM.03.41; S.IA.03.12;
S.IA.03.13; S.IP.03.11;
(Resource: Causes of Motion)
As a review from Kindergarten Science Academic Standard: Physical Science - Force and to determine
prior knowledge, write the term "force" on a piece of chart paper. Determine if students know that a
force is "a push or pull that makes an object move." Remind the students that an object won’t move
without a force of some kind being applied to it. Bring a chair to the front of the room. Push it away.
Have the students tell you whether it was a push or pull that moved it. Now pull the chair toward you.
Ask the students what force moved the chair. Place a variety of classroom objects or toys in the front
of the classroom. Ask for volunteers to come up and push or pull them. Have the class tell you how
the toys were moved. Have students identify gravity as the force that pulls objects toward the Earth.
Play games: floor hockey, paper football, basketball, etc. to discuss forces involved and path and
direction of objects. Include tug-of-war, push/pull heavy and light objects (friction is other force).
Lifting heavy object (gravity is the other force).
At this level, demonstrations include such examples as pushing on a large object such as a boulder
(friction is another force) tug-of-war games (equal pulling on opposite ends of the rope) and lifting a
heavy object (gravity is the other force).
Have students visit the playground and look for opportunities to see how the forces of pushing and
pulling move the playground equipment.
Students have been identifying cardinal directions (N, S, E, W) in Social Studies since first grade, so
teachers may wish to have them use these terms as they compare and contrast the direction in which
an object moves.
2. TLW relate a change in motion of an object to the force that caused the change of
motion.CCSS/CE(s): P.FM.03.37; P.FM.03.38; P.FM.03.42; P.FM.03.43; S.IA.03.12; S.IA.03.13; S.IP.03.11;
S.IP.03.12; S.IP.03.13; S.IP.03.14; S.IP.03.15; S.RS.03.11; S.RS.03.16; S.RS.03.17; S.RS.03.19; P.FM.03.36;
(Resources: Change in Motion; Sneaky Shoe Slide)
Students observe real world situations that involve forces that speed up, slow down, change direction
or stop an object (changes of motion). Students may observe how pushes and pulls can change the
speed or direction of moving objects.
Students discuss ways in which the objects moved and what caused the motion. Create a list of
observations and words that describe the path and direction. Draw a diagram.
In addition to pushes and pulls caused by external sources of mechanical, muscle power, magnets, or
nature (wind and water) students should also make the connection to changes in motion caused by
gravity (objects falling to the Earth when dropped) or friction.
Inquiry - How does changing the object (lighter vs. heavier material made from surface object travels
on) affect motion?
Integrate with physical education by using scooter cars to demonstrate pushes and pulls and changes
in speed (faster, slower) and direction. Relate the speed of an object to the distance it travels in a
standard amount of time. Establish an association or connection between distance, time and speed.
Third grade students are not expected to calculate speed. Students often confuse speed and distance.
Students describe speed as the distance an object travels in a standard amount of time or the amount
of time it takes an object to travel a standard distance. For example, if it takes car A 5 seconds longer
to travel the same distance as car B, car B is traveling at a faster speed. If car A travels a further
distance than car B, in the same amount of time, then car A is traveling at a faster speed.
Students’ measurement abilities include measuring the distance something travels (kilometers,
meters,
centimeters) and the amount of time it takes to travel a certain distance (hours, minutes, seconds).
Measurement tools include meter sticks, rulers, measuring tapes, stop watches, clocks with a
second hand.
Speed descriptions include faster and slower.
3. TLW demonstrate when an object does not move in response to a force it is because another force
is acting on it. CCSS/CE(s): P.FM.03.37; P.FM.03.38;
Sample Demonstrations:
1. Pull an object across various surfaces, e.g., rubber mat, carpet, sandpaper, table top,
concrete, or grass.
2. Use a spring scale to measure the force necessary to move an object, e.g., block of wood or
book. Use a spring scale with Newtons and grams so students can determine the amount of
force applied in Newtons. Students should observe and conclude that different objects require
different amounts (strength) of force to move the object the same distance. They should
demonstrate how the change in motion of an object is related to the strength of the force acting
upon objects with different mass.
3. Use a Friction Block and/or Surface Board (order from Frey Scientific, 1-800-225-FREY). A friction
block can be made with a 2 x 4 block that has different surfaces on different sides. Surfaces could
include sandpaper, rubber mesh drawer liner, carpet, smooth wood, glued-on wax paper, etc. Attach
a hook to one end of the block and attach the block to a spring scale and place on a table. Pull the
scale that is attached to the block to move the block across the table from a stopped position, and
measure the force (in Newtons) needed to start the block moving. This force will vary, depending on
the surface of the friction block that is making contact with the surface on which the block is resting
(the table). Students should be able to feel the effect of friction (force) on the ease/difficulty of
pulling (force). In this way, students demonstrate that when an object does not move in response to a
force, it is because another force is acting on it.
Students at the third grade level are not expected to measure force; they make observations of
changes in motion due to stronger and waker forces.
Record data using charts, tables, and bar graphs.
4. TLW describe how people have contributed to science throughout history and across cultures.
CCSS/CE(s): S.RS.03.19;
Contributions of scientists throughout history and across cultures have contributed significantly to
current scientific thought. Students research and recognize that the contributions of scientists such as
al-Jazari, Isaac Newton, Albert Einstein, the Wright Brothers, and Sakichi Toyoda have contributed to
the science of forces and motion.
Discuss Isaac Newton and his influence on the understanding of force.
Section 2:
TLW explain the properties of light and sound and how people
perceive these forms of energy.
(Gist: Light and Sound)
Enduring Understanding(s)






Light and sound are forms of energy.
Light enables us to see.
Light travels in a straight line and interacts in different ways with matter.
Sound waves enable us to hear.
Sound waves travel in all directions and have different properties.
Vibrating objects produce sound.
Essential Questions




How do sound and light interact with objects?
How do sound and light travel?
How do we perceive light and sound?
What are sound and light?
New Vocabulary
absorption
energy
forms of energy
light source
path of light
pitch
reflection
shadow
sound source
thermometer
vibrations
Concepts & Information
Demonstrate is to show through manipulation of materials, drawings, and written and verbal
explanations that light travels in a straight path and shadows are made by placing an object in a
path of light.
Light travels in straight paths, which move out from the source until they hit or interact with
something. When light strikes an object, it is reflected, passes through or absorbed.
Light entering our eyes and sound entering our ears are our primary ways of learning about our
world. Our brain interprets the signals it receives from our eyes and ears into visual images or
sounds we understand.
Light Energy
– Light is a form of energy that travels in a straight path through space. Light can travel through
a vacuum. Natural light sources include the Sun, lightning and fireflies. Artificial sources include
candles, electric lights and lasers. White light is made up of all colors of the spectrum; red,
orange, yellow, green, blue and violet. We see colorful objects when light is reflected (bounced
off) objects of that color. Other colors are absorbed by the object. A shadow is formed when and
object blocks light.
Sound waves travel out in every direction from a source. When a guitar string is plucked, the
vibrating string pushes against the adjacent air molecules causing them to vibrate. The air
molecules push against neighboring air molecules until the vibrating air molecules reach a
receiver such as an eardrum.
Light energy can be converted to heat or thermal energy when certain materials absorb it.
Dark materials absorb more of the visible spectrum of light. The absorbed light energy is
converted and is released as heat energy. Since more of the spectrum is absorbed there is more
energy that is converted to heat. Light colored materials absorb less and reflect more of the light
spectrum (less energy) so less energy is released as heat.
Dark materials absorb more light energy; light colored materials reflect more light energy.
Sound Energy
– Sound is a form of energy produced when one object vibrates (moves back and forth) causing
the surrounding air to vibrate in a similar way. Sound does not travel through a vacuum but can
travel through solids, liquids, and gases. The vibrating medium transfers sound waves. Related
properties of sound energy are loudness (volume), pitch and vibrations as a source.
Sounds can have a high or low pitch. -Pitch depends on the speed of vibrations. An object that
vibrates very fast sends more vibrations to the ear drum per second, and the brain interprets it as
a high pitch. When an object vibrates slowly, a lower pitch is heard. -Students' experiences
include the plucking of guitar strings of other stringed instruments (high and low), stretching
rubber bands to create high and low pitches.
The Eye and Light – Objects are seen because light is transmitted to the eyes. Light enters
through the cornea, the pupil (surrounded by the iris), and the lens to the retina at the back of the
eye. The sensory nerves in the retina change light energy to nerve impulses that travel along the
optic nerve to the brain.
The Ear and Sound
– Sound is heard because sound waves moving through the air vibrate the ear drum and fine
bones of the middle ear which transfer vibrations to tiny hairs of the inner ear. The auditory
nerve takes nerve impulses from the inner ear to the brain.
Misconceptions for light
A common misconception at this age is that while light is reflected by mirrors, it remains on
other objects.
A common misconception at this grade level is that the eye gathers light.
A common misconception is that we can see in a completely darkened room.
Misconceptions for sound
A common misconception is that sound cannot travel through solids and liquids.
A common misconception is that sound can travel through a vacuum, such as space.
A common misconception is that sound can be produced without using any materials.
A common misconception is that hitting an object harder changes the pitch of the sound
produced.
Real World Context
Light is all around in many different forms. We use a variety of natural and man-made light
sources everyday. Different kinds of lighting such as fluorescent bulbs, mercury-vapor lighting
in parking lots, and the multiple uses of laser light are more energy efficient. The sun is the
major light source for life on Earth. Scientists have developed technology to capture the light
from the sun to be used for solar energy that generates electricity for heating, cooling and
lighting. Light energy can also be stored through technology for future use.
Photography and the use of cameras show how light and the human eye behave. Light is
necessary for sight. Light strikes an object and is reflected for the eye to perceive the image.
Scientists and inventors use the properties of light to make televisions, computer screens, lasers,
and many other tools and devices that are used in homes, hospitals, industry, and agriculture.
Lewis Howard Latimer and Thomas Edison were pioneers in understanding and applying the
properties of light to make useful contributions to society
Lesson Ideas:
1. TLW identify light and sound as forms of energy. CCSS/CE(s): P.EN.03.11; S.IA.03.12;
S.IP.03.11; S.IP.03.12;
(Resources: Radiometer and Light Potential; Sound as Energy)
Introduce the question; Is light a form of energy? With the assistance of the teacher, students use
thermometers in dark colored materials and white/light colored materials placed under a lamp or
sunlight. Students record observations on charts. The activity is repeated two more times for
accurate results. In collaborative groups, students share their ideas about the differences in the
temperatures recorded. They communicate their findings. Using the evidence gathered during the
activity, they conclude that light is a form of energy because the light energy is transformed to
heat energy. There is a change in temperature.
Sound and light energy come from a source and travel in space to other objects. Light and sound
are responsible for much of what we know because they allow us to see and hear.
Use Resource: Radiometer and Light Potential and a radiometer to show how light is a form of
energy. Use Resource: Sound as Energy and a tuning fork to show how sound is a form of
energy.
2. TLW investigate properties of light. CCSS/CE(s): S.IA.03.12; S.IA.03.13; S.IP.03.11; S.IP.03.12;
S.IP.03.13; P.EN.03.21; P.EN.03.22; P.PM.03.51;
(Resources: Colors of Light; Colors of Light Using Diffraction Grating Glasses)
In a discussion, ask students what they already know about light and about sources of light. To
guide the discussion, use questions such as: What happens when the lights are turned on in a dark
room? How are we able to see objects? Can we see without light? What happens when light hits
an object? What is our main source of light? (sun) Record observations and ideas and questions
that are generated on chart paper and post for reference during the unit on light.
Investigate the colors in white light. A prism or diffraction grating with an overhead projector is
used to separate white light into the colors that make it up. Rainbow glasses also are very
effective. The name ROY G BIV is a mnemonic to help remember the order of the colors in the
prism: red, orange, yellow, green, blue, indigo, and violet.
An overhead projector, flashlight and candle comparison demonstrates that light has different
levels of brightness.
Investigations should help students demonstrate that light travels in a straight path.
The guiding question for this activity is: How does light travel? Use flashlights and
approximately six 3x5 index cards with holes per group of students. (Punch holes in the same
spot through five of the cards. Students use the sixth card as a target and try to line up the cards
so that the light hits the target.) Students discover that the cards need to be lined up in a straight
line in order for the light to pass through the holes and hit the target. Students conclude that light
does not bend. Light travels in straight lines. Continue to record observation, ideas and questions
generated during the activity. Record on chart paper for future reference.
Investigations should help students demonstrate what happens to light when it interacts with
matter. Light can be reflected, refracted, transmitted (pass through), or absorbed. Simple
demonstrations can illustrate these properties. Use a mirror to show reflection. The diffraction
grating or prism demonstration above shows refraction.
Students should also investigate and demonstrate the refraction that occurs to light when it
travels from water to air. Use a straw half in water and show how it appears to be bent. Also
observe a straw or other objects in water, out of water. Students are aware of how light passes
through glass.
Place a pencil in a cup of water or through a zip type bag full of water and observe what happens
to the appearance of the pencil. Use a tank of water and have students view objects in the water
from all angles including from under the surface looking up. In collaborative groups, students
discuss their observations.
As questions arise in their discussions, students research the answers. Students create a graphic
organizer or model to demonstrate the path of light as it enters water. Note: Third grade students
do not need to understand that the speed of light varies as it travels through different media.
Third grade students simply make observations.
Students' experiences should include observations of objects in water, out of water, half in and
half out of water. Students may investigate other transparent substances such as alcohol, oil, corn
syrup.
Third graders do not need to understand why light bends (refraction). They only need to observe
that objects appear to bend when observed through different mediums.
Student experiences should include multiple opportunities to use light bulbs and sunlight to heat
a variety of materials including light colored sand vs. soil, light colored paper vs. dark paper,
light colored hat vs.dark hat.
Students' experiences include using a thermometer to compare temperatures in degree Celsius.
The emphasis for third graders is warmer and cooler.
Students design a simple investigation based on a question generated from the “Properties of
Light” chart, i.e. can light be reflected more than one time? They use appropriate tools of
observation and construct simple charts and graphs from data and observations. Students
summarize information and communicate findings.
Students should also demonstrate how some materials are heated more than others by light that
shines on them. Use construction paper of different colors under intense light and feel the
difference in temperature. (Black and white show the most difference in absorption.)
Distribute a mirror to each student. Students observe themselves in the mirror. Instruct students
to move the mirror to the side until they see the person behind them. Ask: Can the person behind
you see your face? Can you see your own face? Students manipulate the mirror and make
observations. Record observations on a chart entitled: “Properties of Light.”
Teacher preparation: Cut a narrow slit (just a few millimeters wide) in the center along one edge
of a 3 x 5 index card (note: black card stock works better). Tape the card over the front of a
flashlight so that the open end of the slit just meets the edge of the flashlight. Turn on the
flashlight and set it on a sheet of white paper on a flat surface. Adjust the flashlight so there is a
narrow beam of light along the length of the paper. Place a mirror without a frame upright at the
end of the paper propped up by a book. Lay the flashlight on a table at one end of the white
paper.
Students shine the light through the slit along the white paper onto the mirror. They should see
both the incoming and the reflected beam on the paper. Have students make observations about
the light as they see it go to the mirror and away from the mirror. What types of things did they
notice? Encourage students to manipulate the flashlight and the mirror.
Trace the incoming and reflected beams of light on the paper. Although students of this age
won’t be able to measure angles and get an accurate drawing of the path of the light being
reflected by the mirror, they should see that it forms angles or triangles that look the same going
from the flashlight to the mirror and away from the mirror. Add to the chart entitled “Properties
of Light” that light can be reflected.
Students discuss and share their ideas of how light travels in a straight path and what happens
when it hits a surface like a mirror. The idea that it travels in straight lines should start to become
apparent. Add to the chart entitled “Properties of Light” that light travels in straight lines.
Student observations of the light activities are recorded in a lab book or science journal. Explain
and create definitions for: reflection, source, path of light. Give descriptive examples of each of
the terms using written words, diagrams and pictures. Record definition examples in student
journals.
As students move through the unit, add the terms: refraction, transparent, translucent, and opaque
to student journals.
Explore the question, How does light behave when it interacts with different objects? Design an
investigation to explore how light interacts with various surfaces. Provide groups of students
with flashlights, mirrors, aluminum foil, glass or clear plastic, waxed paper, etc. As students
explore the materials with their flashlight, they create a chart to record their findings. Through
class discussion, students develop an understanding of transparent, translucent and opaque
objects and whether or not they create shadows. Add to the “Properties of Light” chart that light
can be absorbed or reflected.
Cut out a variety of shapes from opaque material or use a variety of opaque objects. Students use
the shapes to block light and form shadows. They explore shadows by manipulating the objects
on a piece of white paper, using different sources of light. Trace the shadow on the paper and
record observations. Predict the shape of a shadow given a source of light and an object.
3. TLW demonstrate how a shadow is made. CCSS/CE(s): P.EN.03.21; S.IA.03.13; S.IP.03.11;
(Resources: What Makes a Shadow; Me and My Shadow)
Students should demonstrate that shadows are made by placing an object in a path of light.
4. TLW collaboratively investigate the path of light from its source to an object to the eyes.
CCSS/CE(s): P.PM.03.52; S.IA.03.13; S.IP.03.11; S.IP.03.13;
(Resource: Light Investigations)
Ask: Do we need light to see? How do you know? Students record their ideas in student journals.
If appropriate, take students into a room that can be darkened completely. Turn off the lights.
Discuss what they can see. Is the room completely dark? In a darkened room with a mirror (a
bathroom is perfect), students look at their eyes in the mirror with the flashlight on, then off, then
on. They discuss their observations. Students answer the question, How does light get into our
eyes? Using the concepts presented in earlier activities, discuss that light travels in straight lines.
Share ideas that when light hits an object it is reflected and enters our eyes.
We see objects because they either emit light or reflect light.
When light is reflected or bounces off an object, the light waves travel in straight lines until they
reach the eye. The light enters the eye through the pupil and we see the object.
Students should be able to explain that we need light to see objects and that light from a source
reflects off objects and enters our eyes. As students investigate light, relate light to the sense of
sight and the eye as the organ of seeing.
5. TLW investigate properties of sound through experimentation with a variety of sound
sources. CCSS/CE(s): P.EN.03.31; P.EN.03.32; S.IA.03.12; S.IA.03.13; S.IP.03.11; S.IP.03.12; S.IP.03.13;
(Resources: Investigations of Sounds; The Sources of Sound; Sounds of Straws; String
Telephone; Loudness; Picking Up Good Vibrations)
Go outside and have students make observations using their sense of hearing. Have students
make a list of all the sounds they hear and then classify the sounds as natural or man-made
(manufactured).
Ask students to describe their ideas of how sounds are made.
Hold a plastic ruler on a table so that half of the ruler hangs out over the edge of the table. Pluck
the free end of the ruler lightly and again with more force. The ruler vibrates producing a sound.
Students record and discuss observations of the difference in sounds. Move the ruler to a
different length, either longer or shorter, and repeat using the same force when plucking.
Students make observations and discuss the difference in the sounds. How did the length of the
ruler affect the sound? Record observations and create a class chart for questions and ideas about
sound.
Provide a variety of toys that produce sound such as whirling tubes, clackers, buzzers, etc.
Students explore the “Sound Museum” and make observations. Identify how the sounds are
produced.
Have students choose one of the toys or an instrument and explain how it produces sound.
Create operational definitions for the words sound, vibration, and pitch.
Draw a diagram of a high-pitched sound wave and a low-pitched sound wave. Have students
make connections between the diagrams and the sounds from different instruments.
Students make own instruments with rubber bands, string, boxes, straws, etc. Students record and
share what they observe about the various “instruments” they made.
Create drums using different sized containers and materials for the drumhead. Explore tightening
and loosening the drumheads. Students record and share what they observe.
Create straw whistles of different lengths. Students record the highs and lows of the pitch and
compare it with the length of the column of air/straw.
Borrow stringed instruments from the music teacher. Students explore the effects of changing the
length of strings while plucking.
Relate sounds to their sources of vibrations. Use a tuning fork, drinking straw, comb, ruler,
rubber bands, blade of grass, and musical instruments. For example, relate the musical tone
produced by a vibrating guitar string or the sounds of a drum made by the vibrating drum head.
See AIMS Primarily Physics for musical instrument ideas.
Students should distinguish the effects of fast or slow vibrations as pitch.
Also identify the property of loudness (volume).
As students investigate sound, make sure to relate sound to the sense of hearing and the ear as
the organ of hearing.
6. TLW investigate the contributions of scientists who have used properties of sound to aid
in communication and hearing. CCSS/CE(s): S.RS.03.17;
People that lose their sense of hearing rely on hearing aids to pick-up or sense the vibrations of
sound to help them distinguish different sounds and words. Contributions of scientists such as
Thomas Edison, Alexander Graham Bell, Guglielmo Marconi, and Ernest Chladni have used the
properties of sound to design different tools and devices that aid in communication and hearing.
Suggested Instructional Resources
AIMS Primarily Physics
Excellent spectrums can be produced on an overhead projector by using holographic diffraction
grating from Arbor Scientific, PO 2750, Ann Arbor, MI 48106-2750, 1-800-367-6695,
www.arborscientific.com, or Education Innovations at http://www.teachersource.com
Section 3:
TLW demonstrate an understanding that scientific inquiry and
reasoning involves observing, questioning, investigating, recording,
and developing solutions to problems by investigating gravity.
Enduring Understanding(s)
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Gravity is the force that pulls objects toward the Earth.
Inquiry includes an analysis and presentation of findings that lead to future questions,
research, and investigations.
Inquiry involves generating questions, conducting investigations, and developing
solutions to problems through reasoning and observation.
Essential Questions
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How does science help us answer questions about the world around us?
What does it mean to question?
What is gravity?
Why do scientists conduct investigations?
New Vocabulary
contrast
force
gravity
timer
weight
Concepts & Information
Inquiry involves generating questions, conducting investigations, and developing solutions to
problems through reasoning and observation. It includes an analysis of the findings and
communicating those findings with others. In this way, more questions are generated and further
investigations are refined. The scientific knowledge can be applied to new situations to solve
new problems.
Mass is the measure of the material that an object contains. The tool for measuring mass is a
balance, measured in metric units. Mass is not changed due to gravitational pull. Mass is the
amount of material that an object contains. It is measured with a balance which compares
measures of mass. Mass is different from weight.
Weight is the gravitational pull on an object’s mass. The tool for measuring weight is a scale,
measured in customary units. Students describe objects as having more or less pull by the Earth
and more or less weight.
Note: Making the distinction between mass and weight may be difficult for the third grade
student. The term weight may be used in third grade.
Capacity (volume) is the amount a container can hold.
A force is a push or pull (gravity, friction and magnetism). The amount of force needed to move
an object depends on the object’s mass. Forces speed up, slow down, stop or change the direction
of a moving object. Gravity is the attraction, or pulling force, between objects and gravity is the
force that pulls objects towards the Earth. All objects have a gravitational pull. The greater an
object’s mass, the greater its pull on other objects.
Gravity is the attraction, or pulling force, between objects. All objects have a gravitational pull.
Because Earth is so large, it pulls down on all objects. The greater an object’s mass, the greater
its pull on other objects. Students can see the effects of gravity on objects even though gravity
can’t be seen or touched. They can feel the force of gravity in an elevator (feeling more gravity
when ascending and less gravity when descending). Also, students will be aware of an exception
to the "rule" with helium-filled balloons. Be careful when discussing this with students, because
a floating helium-filled balloon is displaying the force of buoyancy, in which the helium floats,
because it is less dense than air. Most third grade students will be aware of the property of
buoyancy but will not understand how it works in relation to gravity.
The term gravity is very abstract. Third grade students do not need to define the term gravity.
They need only to observe that dropped or thrown objects eventually fall to the ground. Some
exceptions are helium and hot air balloons, or objects rising in water. Third graders may be
aware of the exceptions but do not need to understand the science behind it.
Gravity is the attraction between all matter; it is the force that pulls objects toward each other.
The larger the object, the greater the force.
Because of the Earth’s size, the pull of gravity is very apparent.
The downward force of gravity is called weight. Weight is the measure of the pull, or force, of
gravity on an object.
Weight is measured using a scale, whereas mass is measured using a balance.
The emphasis of this expectation is that gravity is the force that pulls objects to the Earth. Weight
is the measure of the pull of gravity. Students describe objects as having more or less pull by the
Earth and more or less weight .
Common Misconceptions
Students may think that the scientific method is linear.
Only large objects have gravitational force.
Energy and force are interchangeable.
Lesson Ideas:
1. Using a balance and metric mass set, TLW measure the mass of objects in grams.
CCSS/CE(s): S.IP.03.12; S.IP.03.14; S.IP.03.15;
Determine if an object measured in grams is heavier, lighter, or the same as another object.
2. Using a balance and a metric mass set, TLW measure the mass of objects in kilograms
and grams. CCSS/CE(s): S.IP.03.12; S.IP.03.14; S.IP.03.15;
Determine if an object measured in both kilograms and grams is heavier, lighter, or the same as
another object.
3. TLW demonstrate scientific processes related to observations of the natural world by
investigating gravity. CCSS/CE(s): P.FM.03.22; S.IA.03.14; S.IP.03.12; S.IP.03.16;
(Resources: Science Inquiry Investigation; Science Investigation Report)
Students will apply measurement skills by participating in a guided inquiry investigation
regarding gravity and the impact of objects of various sizes when dropped. Begin by having
students complete a KWL organizer to identify prior knowledge. (Gravity was taught in
Kindergarten.) Use the Science Inquiry Investigation to have students identify gravity as the
force that pulls objects toward the Earth. Students should generate questions based on their
observations, and construct charts from data and observations (Integrate with Third Grade
Mathematics Academic Standard: Data and Probability - Bar Graphs for collecting and
organizing data and creating, reading, and interpreting bar graphs). Students should also develop
strategies for information gathering and problem solving. They should also demonstrate
scientific concepts through various illustrations, performances, models, exhibits, and activities.
Note: The assessment for this academic standard combines both science and mathematics in one
assessment. Assessment I assesses Math GLCEs only and Assessment J assesses the guided
inquiry investigation. Gravity will be assessed in further depth in Third Grade Science:
Academic Standard - Force and Motion.
Suggested Instructional Resources
Jerry Pallotta, Hershey’s Milk Chocolate Weights and Measures Book, 2003, ISBN
0439388775
Jerry Pallotta, Hershey’s Weights and Measures Book, 2003, ISBN 0613630416